Green to transmissive soluble electrochromic polymers

ABSTRACT

Green to transmissive soluble electrochromic polymers are conjugated polymers having a plurality of repeating units where repeating units are a plurality of substituted dioxyheterocycle based donor groups coupled to an acceptor group. The conjugated polymer absorbs radiation within a first band of the visible spectrum and a second band of the visible spectrum when in a neutral state resulting in a green color and is transmissive when in an oxidized state. The polymers are soluble allowing processing of films and coatings from solution.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 12/740,570, filed Jul. 15, 2010, which is the U.S. national stageapplication of International Patent Application No. PCT/US2008/081599,filed Oct. 29, 2008, which claims the benefit of U.S. ProvisionalApplication Ser. No. 61/000,908, filed Oct. 30, 2007, the disclosures ofwhich are hereby incorporated by reference in their entireties,including any figures, tables, or drawings.

The subject invention was made with government support under the AirForce Office of Scientific Research, Contract No. F9550-06-1-0192. Thegovernment has certain rights to this invention.

BACKGROUND OF THE INVENTION

Polymeric electrochromics capable of a fast and reversible color changeupon electrochemical oxidation and reduction have received aconsiderable attention over the past decade. A particular emphasis hasbeen placed on incorporating the most stable of these electroactivematerials in devices such as windows, mirrors (rear-view/side-viewmirrors for cars) and displays, for anticipated industrial andcommercial applications. While a number of neutral state red and blueabsorbing conjugated polymers have been synthesized and integrated intoelectrochromic devices, attempts at synthesizing saturated greenpolymers chemically or electrochemically, which can switch to atransmissive state, have met with limited success due to the complexnature of the required absorption spectrum that must contain at leasttwo bands in the neutral state of the material.

To date, only one article reports the existence of a green conjugatedpolymer with a transmissive state (with a blue hue) upon oxidation.(Durmus et al., Chem. Commun., 2007, 3246-3248). However, this materialis prepared by an electrochemical polymerization/film deposition anddoes not show any solubility/proccessability making it difficult to beintegrated into devices, restricting the scope of possible applications.

Accordingly, soluble neutral state green conjugated polymers with highelectrochromic contrasts, fast switching times and highly transmissiveoxidized states would be a desirable improvement in the field ofconjugated polymers. Additionally, materials that are solutionprocessable would provide advantages in a wide range of applications.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention are directed to a conjugated polymerconstructed with a plurality of repeating units where the repeatingunits have a plurality of substituted dioxyheterocycle based donorgroups coupled to an acceptor group. The conjugated polymer absorbsradiation within a first band of the visible spectrum and a second bandof the visible spectrum when in a neutral state but is transmissive inthese bands in an oxidized state. The absorbance of radiation within thefirst and second bands in the oxidized state is less than in the neutralstate to the extent, often by 200% or more, such that one can discernthe polymer as colored in the neutral state but of little or no color inthe oxidized state. The first absorption band can have a visibleabsorption maximum at a wavelength below about 500 nm and the secondabsorption band can have a visible absorption maximum at a wavelengthabove about 550 nm and a local minimum between 480 and 580 such that theneutral state colored polymer is green in appearance.

The polymer can be soluble in one or more solvents, for examplemethylene chloride, chloroform, tetrachloroethane, tetrahydrofuran,dioxane, benzene, toluene, xylenes, chlorobenzene, dichlorobenzene,pyridine, ethyl acetate, butanol, ethanol, methanol, acetonitrile,acetone, isopropanol, water and mixtures thereof. The polymer can thenbe prepared and processed into films or coatings from solution. Thedioxyheterocycle of the polymer can be a dioxythiophene, such as analkylenedioxythiophene, for example a 3,4-propylenedioxythiophene. Theacceptor group is an electron poor aromatic unit such as a substitutedor unsubstituted benzothiadiazole group, thiadiazoloquinoxaline group,quinoxaline group, thienothiadiazole group, thienopyrazine group,pyrazinoquinoxaline group, benzobisthiadiazole group orthiadiazolothienpyrazine group.

In many embodiments the conjugated polymer can be envisioned by therepeating unit is a sequence of structural formula III:*—Z_(q)—Y-E_(r)-X-E_(r)-Y—Z_(q)—*  IIIwhere X is an electron poor aromatic unit, E is an electron richconjugated unit, Y is a substituted dioxyheterocycle, Z is a conjugatedunit, and q and r are 0, 1, 2 or 3. The unit Y can be a substituteddioxythiophene that can be an alkylenedioxythiophene substituted with atleast one linear or branched aliphatic carbon chain that can have one ormore heteroatoms within the chain as indicated by thepropylenedioxythiophene (ProDOT) in formula II:

where X is an electron poor aromatic unit, E is an electron richconjugated unit, Z is a conjugated unit, q and r are 0, 1, 2 or 3, andR¹⁰, R¹¹, R¹² and R¹³ are the same or different and at least one of R¹⁰,R¹¹, R¹² and R¹³ includes a linear or branched aliphatic carbon chainthat optionally includes one or more heteroatoms. The electron pooraromatic unit, X, can be a substituted or unsubstituted benzothiadiazolegroup, thiadiazoloquinoxaline group, quinoxaline group, thienothiadiazolgroup; thienopyrazine group, pyrazinoquinoxaline group,benzobisthiadiazole group or thiadiazolothienopyrazine group. Forexample, in embodiments of the invention the electron poor aromatic unitcan be a 2,1,3-benzothiadiazole group (BTD). The electron richconjugated unit E can be a substituted or unsubstituted thiophene and Zcan be a substituted or unsubstituted dioxythiophene group.

Another embodiment of the invention involves a method of forming aconjugated polymer, which includes steps of reacting two donor compoundshaving a substituted dioxyheterocyclic moiety with a conjugated acceptorcompound having an acceptor moiety to form a polymerizable unit, whichis an oligomer where dioxyheterocycle based donor groups are attached toan acceptor group. A plurality of these oligomeric polymerizable unitscan then be linked covalently to form the conjugated polymer, where theconjugated polymer absorbs radiation within a first band of the visiblespectrum and a second band of the visible spectrum when in a neutralstate and upon oxidation the polymer is transmissive as described above.The polymer is soluble in at least one solvent. In one embodiment thedioxyheterocyclic moiety can be a dioxythiophene moiety having acoupling moiety which can be an organometallic substituent such as anorganotin substituent, organoboron substituent, organomagnesiumsubstituent, organozinc substituent, or organosilane substituent and theconjugated acceptor compound contains a pair of complementary halogenfunctional groups symmetrically situated on the conjugated acceptorcompound. Conversely, in another embodiment, a pair of organometallicsubstituents can be attached to the conjugated acceptor compound and ahalogen group can be the coupling moiety of the dioxyheterocyclicmoiety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows absorbance spectra of polymers (a) 6a, (b) 6b, (c) 9 and(d) 12 respectively where thin films were cast onto ITO from toluene(6a, 6b, 9) or chloroform (12) and electrochemically oxidized in a 0.1 Msolution of LiBF₄ in Acetonitrile.

FIG. 2 shows relative luminance measured on thin films of Polymers 6a(P([ProDOT-OOct₂]₂-BTD)) (●), 6b (P([ProDOT-OEtHex₂]₂-BTD)) (▴), 9(P([ProDOT-OOct₂-Th]-BTD)) (▪) and 12 (P([ProDOT-OOct₂-Th]₂-BTD)) (▾).Experiments were carried out using solid thin films spray cast onto ITOfrom toluene (6a, 6b, 9) or chloroform (12).

FIG. 3 shows photographs of the neutral and oxidized polymers (a) 6a(P([ProDOT-OOct₂]₂-BTD)), (b) 6b (P([ProDOT-OEtHex₂]₂-BTD)), (c) 9(P([ProDOT-OOct₂-Th]₂-BTD)) and (d) 12 (P([ProDOT-OOct₂-EDOT]₂-BTD)) assolid thin or/and thick films spray cast onto ITO from Toluene (6a, 6b,9) or Chloroform (12).

DETAILED DESCRIPTION OF THE INVENTION

One embodiment of the invention is a new and efficient route towardssynthesizing novel, soluble conjugated polymers that are green in theneutral state and high transmissive in the oxidized state. According toan embodiment of the invention, the soluble conjugated polymer providesone or more of the following advantages: high optical contrast in thevisible region; outstanding electrochemical switching properties; chargetransport properties, as desired for green colored solar cells; and theability to be processed into electrochromic devices using convenientdeposition methods, such as spin coating, roll-to-roll coating, spraycasting, and various methods of printing (e.g. ink jet printing).

To achieve a neutral state green polymer, absorption in the red and theblue regions of the visible spectrum is required. Fine tuning of theenergy gap, as well as introduction of an adequate set of absorptionbands in the electromagnetic spectrum, is achieved by the choice of thestructure of the repeating units that compose the conjugated portion ofthe polymer. Structural parameters are controlled to achieve the desiredoptical properties and proccessability for this new family of solublepolymers. Careful analysis and comparison of the bathochromic shiftoccurring upon polymerization can allow determination of an expectedabsorption spectrum of a single polymerizable unit to be synthesized andpolymerized. This polymerizable unit comprises electron donating andaccepting moieties that constitute the backbone of the electrochromicpolymer.

In embodiments of the invention, a dioxythiophenes moieties having atleast one solubilizing chain substituted thereon comprise the donatingmoieties within the polymerizable units employed to form the polymers.Any solubilizing chains can be employed that provide a desiredsolubility during processing. In one embodiment, the solubilizing chainscan be alkoxy solubilizing chains (linear or branched), which allowprocessing into solid thin film by solution casting and can enhancetransmissivity of the oxidized state. For a polymeric materialtransmitting/reflecting green light, obtaining highly transmissivecontrasts upon oxidation requires simultaneous and efficient bleachingof the two absorption bands that occur in the blue and red portions ofthe visible spectrum.

The soluble conjugated polymers of embodiments of the invention areprepared by coupling dioxyheterocyclic donor moieties with acceptormoieties via coupling reactions. Coupling reactions that can be used,include, but are not restricted to: Stille coupling, Kumada coupling,Hiyama coupling, Negishi coupling and Suzuki coupling.

In one embodiment of the invention Stille coupling is employed as thecoupling reaction. In this embodiment, the polymerizable units areprepared using stannylated dioxythiophenes, which can be prepared usingany suitable technique, followed by an oxidative polymerization of theunits. The units are appropriately functionalized oligomers of donor andacceptor moieties that in combination yield the electrochromicproperties of the green to transmissive polymers. In an embodiment, thestanylated dioxythiophene compounds can be 3,4-propylenedioxythiophenescompounds of formula 3 in Scheme 1, below, shown as trimethyl tin(—SnMe3), or any suitable organotin substituent, such as triethyl tin(—SnEt₃) or tributyl tin (—SnBu₃). The organotin substituent can bereplace with any suitable substituent, such as an organoboron,organomagnesium, organozinc, or organosilane substituent. The R groupsof formula 3 can be the same or different and can be chosen to be alinear or branched aliphatic carbon chain, or a carbon chain containingaromatic moieties, wherein the aliphatic or aromatic carbon chain canoptionally comprise one or more heteroatoms (e.g., oxygen or nitrogenatoms) or functional groups chosen from oligoether groups, ester groups,amide groups, carboxylic acid groups, sulfonate groups, amine groups andother polar functional groups. The entire CH₂OR group can be replacedwith an alkyl or aryl chain and one of the CH₂OR groups can be replacedwith a hydrogen substituent. A general formula for a stanylated3,4-propylenedioxythiophene is given in Formula I:

where R groups are the same or different and comprise linear or branchedaliphatic carbon chains and can optionally comprise one or morefunctional groups chosen from oligoether groups, ester groups, amidegroups, carboxylic acid groups, sulfonate groups, amine groups and otherpolar functional groups and R′ comprises an alkyl group.

An embodiment of the invention includes preparing stannylatedalkylenedioxythiophenes, as shown in Scheme 1, above, where amonostannylated bis-alkoxymethyl substituted 3,4-propylenedioxythiophene(3), which can be coupled into a polymerizable unit. The synthesisbegins with a facile nucleophilic substitution of alkoxy derivatives(solubilizing group) for Br of compound 1, which is shown as aWilliamson etherification in N,N-dimethylformamide (DMF) where a sodiumalkoxide is formed by the reaction of an alcohol with sodium hydride toform compound 2. The R groups of scheme 1 are shown as being octyl or2-ethylhexyl, although any suitable linear or branched alkyl groups,such as C2 to C30 alkyl groups, can be employed. Appropriate reactionconditions for etherification reactions are known to those skilled inthe art. Other reactions can be employed to form appropriatelysubstituted 3,4-propylenedioxythiophenes for use as donor moieties toform the polymerizable units.

The resulting symmetrical alkoxy substituted compound 2 of Scheme 1 ismonolithiated using a suitable organolithium reagent, such as, forexample, n-butyllithium, t-butyllithium, or methyllithium. Othersufficiently basic reagents can be employed for the preparation of anorganometallic intermediate, where the metal can be, for example, anyalkali or earth alkali metal, for the preparation of the monostannylatedproduct 3. The reaction can be performed in any suitable organicsolvent, generally a polar aprotic solvent such as tetrahydrofuran(THF). The resulting compound is then monostannylated by replacing theresulting lithium substituent with an organotin substituent using anysuitable tin containing reagent, such as trimethyltin chloride ortributyltin chloride, to afford the relatively air-stable compound 3 inhigh yield. Other stannylated alkylenedioxythiophenes or dioxythiophenescan be prepared in an analogous fashion to that illustrated in Scheme 1by employing the appropriate starting compound. Although anetherification reaction is not necessary for many embodiments of thereaction, appropriate groups to achieve solubility are needed. The donormoiety used in the coupling reaction does not necessarily require thepresence of a substituent to impart solubility; however, at least onemoiety in the polymerizable unit has a substituent to impart solubilityto the polymer.

The stanylated alkylenedioxythiophenes can then be used to formoligomers having alkylenedioxythiophene end groups, which are thepolymerizable units. This process includes mixing the stanylatedalkylene dioxythiophenes with an additional compound, which contains atleast one acceptor moiety. For example, in an embodiment, compound 3 canreact with one or more halogenated compounds containing the acceptormoiety.

Scheme 2 illustrates an example of a method according to an embodimentof the invention that progresses through the construction of soluble andsymmetric conjugated oligomers, polymerizable units, having donor andacceptor moieties and through the polymerization of the oligomers toyield linear conjugated polymers. Table 1 discloses the characterizationof a number of polymers according to embodiments of the invention. Asillustrated in Scheme 2, a Stille reaction can be used to couplestannylated compound 3 with dibrominated acceptor containing species 4,7 or 10. Other halogens, such as chlorine, iodine, or even fluorine canbe used in place of the bromine on the acceptor compounds. The acceptorsare generally, but not necessarily, symmetrically halogenated wherehalogens are positioned on equivalent opposite sites of the acceptorcompounds, as shown for compounds 4, 7 and 10. Stille reaction processesare well known in the art, and can be carried out using, for example, aPalladium(0) or Palladium (II) catalyst. In many embodiments, thereaction is carried out under air and moisture-free conditions tomaximize the reaction yields. Soluble oligomers 5, 8 and 11 can beisolated by various techniques, including, for example, columnchromatography using silica as the stationary phase and varying theratios of solvents employed for elution. Such solvents can include, forexample, mixtures of hexanes, dichloromethane and ethyl acetate.

The oligomers can be polymerized in a step-growth fashion where thealkylenedioxythiophene end groups self-condense to form the conjugatedpolymer. For example, as illustrated in Scheme 2, the target oligomers5, 8 and 11 can be self-condensed in chloroform, or other suitablesolvent, through the low oxidation potential 3,4-propylenedioxythiophenechain-ends using ferric chloride as an efficient oxidative agent toafford fully conjugated and well-defined electroactive polymers 6a, 6b,9 and 12 as indicated in Table 1. Polymer purification can be carriedout by precipitation in MeOH, reduction in chloroform using hydrazinemonohydrate followed by a 48 hours Soxhlet purification. (see Table 1)Although the “R” groups of scheme 2 are shown as being octyl or2-ethylhexyl, any suitable linear or branched alkyl groups, such as C2to C30 alkyl groups, can be employed to enhance proccessability, finetune the color, including the hue and saturation of the green color,enhance transmissivity of the oxidized form, and modify the solid film'smorphology.

TABLE 1 GPC Estimated Molecular Weights in THF, Isolated Yields for thePolymerizations, Elemental Analysis of the Copolymers 6a(P([ProDOT-OOct₂]₂-BTD)), 6b (P([ProDOT- OEtHex₂]₂-BTD)), 9(P([ProDOT-OOct₂-Th]₂-BTD)) and 12 (P([ProDOT-OOct₂-EDOT]₂-BTD)). M_(w)Avg. no. of EA (Calcd/Found) Polymer M_(n) (g/mol) (g/mol) PDI repeatunits Avg. no. of rings Yield (%) C H N P([ProDOT-OOct₂]₂-BTD) 1470032150 2.2 15 45 75  66.5/66.42 8.57/8.64 2.77/2.79P([ProDOT-OEtHex₂]₂-BTD) 27800 59000 2.1 27 81 73  66.5/66.21 8.57/8.482.77/2.73 P([ProDOT-OOct₂-Th]₂-BTD) 18900 60300 3.2 16 80 88 65.38/66.087.72/7.75 2.38/2.21 P([ProDOT-OOct₂-EDOT]₂-BTD) 10300 17800 1.7 8 40 8363.22/62.88 7.33/7.27 2.17/2.28

Schemes 3, 4 and 5 illustrate other embodiments of the invention forpreparing neutral state green polymers with transmissive oxidized statesusing the efficient synthetic strategy illustrated in Scheme 2. Scheme 3shows the synthesis of a series of trimers differing by the nature ofthe acceptor core incorporated to the polymerizable unit. As illustratedin Scheme 3, other acceptor units that may be used rather than or inaddition to the dibrominated 2,1,3-benzothiadiazole, 4, (Scheme 2) witha thiadiazoloquinoxaline derivative (A), a quinoxaline derivative (B) ora thienothiadiazol (C), for example. Other acceptor units that can beused in embodiments of the invention include thienopyrazine derivatives,pyrazinoquinoxaline derivatives, benzobisthiadiazoles andthiadiazolothienopyrazines.

Scheme 4 shows other polymers according to embodiments of the inventionwhere the acceptor core is part of a pentameric polymerizable unit.These pentameric polymerizable units can be oxidatively polymerizedusing the conditions of Scheme 2.

Scheme 5 illustrates an embodiment of the invention that involvesreacting 3,4 propylenedioxythiophene compounds with halogenated compoundthat includes the acceptor moiety, in the manner described above whereA, B, and C are displayed in Scheme 3, to produce an oligomer that issubsequently halogenated to form an intermediate to prepare apolymerizable unit. A second alkylenedioxythiophene compound is reactedwith the halogenated intermediate to form an oligomeric polymerizableunit, which can be coupled to form the conjugated polymer. The secondalkylenedioxythiophene compound can be, for example, anethylenedioxythiopene or a propylenedioxythiophene that has beenstannylated for reaction with the halogenated oligomers, as shown inScheme 5. In addition to the alkylenedioxythiophenes illustrated inScheme 5, other dioxyheterocycles can also be employed, for example,3,4-alkylenedioxypyrroles, 3,4-alkylenedioxyfurans, and3,4-alkylenedioxyselenophenes. Suitable examples of dioxyheterocyclesthat can be employed are disclosed in Reynolds et al. U.S. Pat. No.6,791,738, Sep. 14, 2004.

The chemistry outlined in Schemes 1-5 illustrate how the opticalproperties can be controlled by the nature of the conjugated backbone byvarying the thiophene-based donors and the acceptors. Although thepolymers illustrated above have linear and branched alkyl groups assubstituents to provide organic solvent solubility and proccessability,in other embodiments, polar or ionic side chains can be employed. Forexample, any of the R, R¹ and/or R² groups of the compounds shown inSchemes 1-5 can include oligoether, ester, amide, carboxylic acid,sulfonate, amine, phosphonic acid and other polar functionalities.Compounds including such R, R¹ and R² groups can be made using theproposed chemistry or modified chemistry, as would be readily understoodby one of ordinary skill in the art. Ionic or highly polar pendantgroups can provide solubility and proccessability in water or polarsolvents which can permit electrochromic switching in water basedelectrolytes and can allow polymers to be adsorbed onto oxide surfacesof electrochromism and titania based solar cells (Graetzel Cells).

In another embodiment of the invention, ester functionalized PProDOTscan be used as the donors where after processing into films the estercan be hydrolyzed or otherwise converted to alcohols and carboxylicacids, or their derivatives, which allows for the conversion of thesoluble films according to embodiments of the invention to insolublefilms, as is disclosed in Reynolds et al., Published InternationalApplication WO/2007/087587, Aug. 2, 2007, incorporated herein byreference in its entirety, and Reeves et al., Macromolecules 2007, 40,5344, incorporated herein by reference in its entirety. In this manner,insoluble green to transmissive films can be formed from the solublegreen to transmissive films according to an embodiment of the invention.

In the above exemplary embodiments, the dioxyheterocyclic donor moietiesare included in activated coupling reagents that react with halogenatedcompounds including acceptor moieties. In alternative embodiments, theacceptor moieties can be part of the activated coupling reagents and thedioxyheterocyclic donor compounds can have halide functionality forcoupling into polymerizable units. For example, instead of beinghalogenated, the acceptor compounds described above can include acoupling group selected from the group consisting of organotinsubstituents (including any of the organotin groups described above),organoboron substituents, organomagnesium substituents, organozincsubstituents, and organosilane substituents. Such coupling groups can bepositioned, for example, to replace the two halogen functional groups ofthe above illustrated acceptor compounds. This acceptor compound can becoupled with a dioxyheterocycle based donor compounds, as describedabove, where a monohalogen group allows coupling to the difunctionalizedacceptor compound described above.

The resulting polymers formed from the above described methods comprisea plurality of repeating units, which comprise at least two substituteddioxyheterocycle based donor group coupled to an acceptor group.Suitable examples of dioxyheterocyclic groups can be any of thedioxythiophene groups disclosed herein, as well as3,4-alkylenedioxypyrrole, 3,4-alkylenedioxyfuran,3,4-alkylenedioxyselenophene, 3,4-alkylenedioxytelurophene or otherdioxypyrrole, dioxyfuran, dioxyselenophene, or dioxytelurophene groups.Suitable dioxyheterocyclic groups include those derived from thedioxyheterocylces disclosed in Reynolds et al., U.S. Pat. No. 6,791,738,Sep. 14, 2004. In one embodiment, the dioxyheterocycle groups employedto form the repeating units include 3,4-propylenedioxythiophenes. Forexample, the repeating units can have a general formula II:

where X can be chosen from any suitable electron poor acceptor group.The X groups can be substituted or unsubstituted benzothiadiazolegroups, thiadiazoloquinoxaline groups, quinoxaline groups,thienothiadiazol groups, thienopyrazine groups, pyrazinoquinoxalinegroups, benzobisthiadiazole groups or thiadiazolothienopyrazine groups.The E groups can be any suitable electron rich conjugated unit, and theZ groups can be chosen from any suitable conjugated unit. Suitableconjugated units for both E and Z include substituted or unsubstitutedthiophene groups, alkylenedioxythiophene groups, such as substituted orunsubstituted ethylenedioxythiophene groups and propylenedioxythiophenegroups, as well as any of the other dioxyheterocycle groups disclosedherein; q and r can be 0, 1 or 2; and R¹⁰ to R¹³ can be the same ordifferent and can be chosen to be a linear or branched aliphatic carbonchain that can optionally comprise one or more heteroatoms (e.g., oxygenor nitrogen atoms) or functional groups chosen from oligoether groups,ester groups, amide groups, carboxylic acid groups, sulfonate groups,amine groups and other polar functional groups. In one embodiment, R¹⁰,R¹¹, R¹² and R¹³ can each be an —R′OR″ group, where R′ can be a methyl,ethyl or propyl and R″ can be a linear or branched C₂ to C₃₀ alkyl, suchas octyl or 2-ethylhexyl. In an embodiment, R¹⁰, R¹¹, R¹² and R¹³ can bechosen to be the same substituent.

In another embodiment of the invention, repeating units can have ageneral formula III:*—Z_(q)—Y-E_(r)-X-E_(r)-Y—Z_(q)—*  IIIwhere X, E, Z, q and r are defined as above for formula I; and where Yis any suitable substituted dioxyheterocylce. For example Y can be adioxythiophene, such as an alkylenedioxythiophene substituted with atleast one linear or branched aliphatic carbon chain that optionallycomprises one or more heteroatoms.

The X, E and Z groups of Formulae I and II can include any suitablesubstituents which can be positioned on any possible substituent site ofthe ring structures of these compounds. Examples of suitablesubstituents can include any of the R¹⁰ to R¹³ substituent groupsdisclosed herein. One of ordinary skill in the art would readily be ableto determine suitable substituents and positioning of the substituentsfor these groups.

The number average molecular weight of the conjugated polymers of thepresent application can vary widely, depending on the particularrepeating units employed, and the processing parameters used to form thepolymers. Exemplary number average molecular weights can range fromabout 3000 g/mol to about 100,000 g/mol, as measured by gel permeationchromatography, although polymers having number average molecularweights outside of these ranges can also be formed.

Materials and Methods

FIG. 1 characterizes the optical properties of polymers that weresynthesized (6a, 6b, 9, 12) and their electroactivity uponelectrochemical oxidation. As expected for a neutral state greenpolymer, all materials characterized showed two absorption bands in thevisible region of the electromagnetic spectrum, including a first,moderately high absorption peak in the blue portion (below about 500 nm)and a second absorption peak that is generally higher than the firstpeak (indicating intense absorption) in the orange to red portion (aboveabout 580 nm), with very little or no overlap in the green region (about480 to about 580 nm), so that a minimum absorption point occurs betweenthe first and second peaks in the green region. For all materialscharacterized, these two absorption bands bleached simultaneously uponoxidation and a new absorption band arises in the near infrared ascharge carriers are formed (polarons and bi-polarons). In embodiments,the intense bleaching of the two π-π* transitions observed, as well asthe quasi-absence of residual tail of the near infrared absorption bandsinto the visible, are observed and the polymer has a high transmissivityof the oxidized state. Taking the onset of absorption of the mostintense absorption band as a reference for calculation, the opticalenergy gaps of these materials were found in the range 1.43-1.54 eV, andcan therefore be considered to be “Narrow Band-Gap” polymers.

FIG. 2 shows the relative luminance measured under constant illuminationfrom thin films of polymer that were spray cast onto ITO and submittedto progressive electrochemical oxidation. An average of 30% of opticalchange upon oxidation characterizes this family of polymers. While therelative luminance of polymer 12 reaches the moderate value of 73%,polymer 6b shows outstanding transmissivity upon oxidation with arelative luminance value reaching 84% in its fully oxidized state. Thephotographs reproduced in FIG. 3 illustrate this difference where allmaterials have been photographed in their neutral state (left) and intheir fully oxidized state (right) as thin films (top) and/or thickerfilms (bottom). While polymers 6a and 6b reflect a rather “aquamarine”(blue-green or persian green) color in their neutral state, polymer 9can be considered “pine green”. The more red-shifted polymer 12 seems tooffer a green certainly more “olive-like” (forest green) seemingly dueto a residual dark-yellow reflection. Table 2 summarizes the colorcoordinates of all synthesized materials as well as the potentials atwhich the materials undergo optical changes. Examples of neutral stategreen colors that can be achieved using the conjugated polymers of thepresent application can include the range of colors defined by theCIELab color system having “L” values ranging from about 71 to about 80;“a” values ranging from about −15 to about −23; and “b” values rangingfrom about −11 to about 14, although green colors outside of this rangecan also be achieved.

TABLE 2 Colorimetric Results for the Neutral and Oxidized Polymers 6a(P([ProDOT- OOct₂]₂-BTD)), 6b (P([ProDOT-OEtHex₂]₂-BTD)), 9(P([ProDOT-OOct₂-Th]₂-BTD)) and 12 (P([ProDOT-OOct₂-EDOT]₂-BTD)).Polymer Film Charge State E (V) L a b Observed ColorP([ProDOT-OOct₂]₂-BTD) N 0 80 −22 −10 Persian Green O 0.8 93 −2 0Transmissive-Grey P([ProDOT-OEtHex₂]₂-BTD) N −0.05 80 −23 −11 PersianGreen O 0.7 94 −1 0 Transmissive-Grey P([ProDOT-OOct₂-Th]₂-BTD) N −0.3575 −15 1 Pine Green O 0.75 91 −3 −3 Transmissive-Clear BlueP([ProDOT-OOct₂-EDOT]₂-BTD) N −0.6 71 −19 14 Forest Green O 0.8 89 −5 −5Transmissive-Clear Blue

The conjugated polymers of the present disclosure can be employed in avariety of electronic devices. Suitable examples of such devices includeelectrochromic windows, mirrors and displays; SolarTurf, or artificialturfs that can harvest solar energy and generate electricity; CommonPhotovoltaic Devices; Electronic paper; Anti-Stat Conductors andTransparent Conductors; and Field Effect Transistors, supercapacitors,batteries, and other electronic components.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

All patents, patent applications, provisional applications, andpublications referred to or cited herein, supra or infra, areincorporated by reference in their entirety, including all figures andtables, to the extent they are not inconsistent with the explicitteachings of this specification.

It should be understood that the examples and embodiments describedherein are for illustrative purposes only and that various modificationsor changes in light thereof will be suggested to persons skilled in theart and are to be included within the spirit and purview of thisapplication.

We claim:
 1. A conjugated polymer, comprising:

(P([ProDOT-OOct₂-EDOT]₂-BTD)), wherein is the average number ofrepeating units.
 2. A conjugated polymer, wherein the polymer comprises:

where R¹ and R² are independently linear or branched alkyl, wherein n isthe average number of repeating units.
 3. A conjugated polymer, whereinthe polymer comprises:

where R¹ and R² are independently linear or branched alkyl, wherein n isthe average number of repeating units.